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WO2023281280A1 - Semences enrobées et procédé de préparation de semences enrobées - Google Patents

Semences enrobées et procédé de préparation de semences enrobées Download PDF

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Publication number
WO2023281280A1
WO2023281280A1 PCT/GB2022/051777 GB2022051777W WO2023281280A1 WO 2023281280 A1 WO2023281280 A1 WO 2023281280A1 GB 2022051777 W GB2022051777 W GB 2022051777W WO 2023281280 A1 WO2023281280 A1 WO 2023281280A1
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WIPO (PCT)
Prior art keywords
coating
seeds
nanoclay
seed
forming polymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/GB2022/051777
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English (en)
Inventor
Alicja DZIECIOL
Naomi Brown
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Silvibio Ltd
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Silvibio Ltd
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Filing date
Publication date
Application filed by Silvibio Ltd filed Critical Silvibio Ltd
Priority to GB2401738.6A priority Critical patent/GB2623708A/en
Publication of WO2023281280A1 publication Critical patent/WO2023281280A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes

Definitions

  • the present invention relates generally to coated seeds and methods for preparing coated seeds for providing increased hydration and nutrient delivery to the seeds.
  • the present invention relates to swellable seed coatings comprising a hydrogel forming polymer and a nanoclay.
  • Seed coatings may be used to protect and provide a reservoir for water and nutrients that can provide protection against environmental stresses such as water stress, and can provide a more reliable supply of nutrients to the seed.
  • a coating composition comprising a hydrogel forming polymer and a nanoclay can be used to provide a particularly effective seed coating, having advantageous mechanical properties as well as providing an effective reservoir for water and nutrients.
  • a method of coating seeds comprising: providing a coating composition comprising a mixture of a hydrogel forming polymer and a nanoclay; and coating seeds with the coating composition.
  • the coating of the seed may absorb water from its environment and swell to form a hydrogel, storing water in the immediate vicinity of the seed to provide a local water reservoir around seeds and young seedings to protect them from water stress (e.g. excess water or water-deficiencies), whilst also providing a local source of sustained release nutrients.
  • Nutrients and other functional components such as biostimulants, fungicides or microbicides may also be provided in the coating of the seed to provide additional functions in the immediate area of the seed.
  • hydrogel forming polymer with a nanoclay has been found to be particular advantageous for the formation of seed coatings, and are believed to provide an optimal balance of properties required of seed coatings, including, for example, water- absorption potential, mechanical strength, viscosity, matrix stability, abrasion/runoff resistance, ability to physically encapsulate nutrients or biostimulants, ability to ionically bind nutrients, nutrient diffusability, and nutrient releasability (for example providing a slow/sustained release profile).
  • the formation of a hydrogel in the presence of the nanoclay can provide a formulation where the nanoclay at least partially acts as a cross-linking agent in the hydrogel polymer to enhance the mechanical properties of the swollen hydrogel.
  • the ion-exchange sites within the nanoclay structures may serves as a host for ionically binding guest nutrients, where such binding is stronger than the physical encapsulation afforded by the hydrogel polymer alone, and thus imparts slower/sustained release of nutrients from the hydrogel coating.
  • nanoclays increases surface area of the clay and provides a coating composition that is better able to adhere to and provide a close bond to the surface of the seed.
  • nanoparticulate clay is better able to enter and stick within small crevices on the seed so as to form a hydrogel coating that is more closely bound to the seed, which may also improve the efficacy of providing nutrients or other compounds from the hydrogel coating to the seed.
  • the hydrogel forming polymer may be any suitable hydrogel forming polymer.
  • the hydrogel forming polymer may suitably form a hydrogel alone or may form a hydrogel in combination with the nanoclay and/or an additional cross-linking agent.
  • the hydrogel forming polymer is selected from synthetic polymers such as polyvinylpyrrolidone, polyacrylate, polyacrylamide, poly(acrylamide-co-acrylate), poly(ethylenimine), poly(2- dimethyl(aminoethyl)methacrylate) or poly(l-lysine), biopolymers such as alginate, chitosan, nanocellulose carboxylic acid or carboxymethyl cellulose, hydroxyl propyl methyl cellulose, guar gum, silk tein, xanthan gum, gelatin, carrageenan, or combinations thereof.
  • the hydrogel forming polymer is selected from one or more biopolymers and polyvinylpyrrolidone.
  • the hydrogel forming polymer comprises or consists essentially of one or more biopolymers, preferably the hydrogel forming polymer comprises or consists essentially of alginate or chitosan, or a combination thereof.
  • Nanoclay may comprise any suitable nanoclay such as are known in the art.
  • Nanoclays may typically be provided in the form of a natural or synthetic clay mineral that is exfoliated, for example to form nanoplates, and it will be appreciated that nanoclays may be produced from existing clay materials or in the case of synthetic clays may be directly synthesised in the form of the nanoclay.
  • Nanoclays may, for example, comprise plate-like nanocrystals that may be less than 5 nm (typically approximately 1 nm) in thickness and approximately 20 to 2000 nm in diameter.
  • the nanoclay may nonetheless be provided in a dry power form in which agglomerates have a D10 less than about 10 pm, D50 less than about 50 pm, D90 less than about 150 pm and D98 of less than about 300 pm (particle size may be measured, for example, by laser diffraction as is known in the art).
  • the nanoclay may suitably also be provided with a liquid carrier, for example in the form of an aqueous suspension or solution.
  • Exfoliation of clay materials to form nanoclays may be performed by any suitable method, and may, for example, comprise stirring and ultrasonication in a liquid medium, or may comprise physical grinding such as by ball milling. Exfoliation of clay materials is described, for example, in Ting Ting Zhu et al. , “Exfoliation of montmorillonite and related properties of clay/polymer nanocomposites” , Applied Clay Science, 2019, 169, 48-66.
  • Nanoclays may be formed from natural or synthetic clays and may include modified nanoclays such as organically modified nanoclays, which may be suitably be formed from organoclay materials, which may be formed by integrating organic functionality during synthesis of the clay or by surface modification.
  • modified nanoclays such as organically modified nanoclays (such as amine functionalised nanoclays) from organoclays is, for example, described in “T. Okamoto et al., Self-assembly of colloidal nanocomposite hydrogels using 1D cellulose nanocrystals and 2D exfoliated organoclay layers, Gels, 2017, 3, 11”; “J. E.
  • the nanoclay may comprise any suitable clay material, for example a natural or synthetic phyllosilicate clay.
  • the nanoclay comprises or consists essentially of montmorillonite, saponite, hectorite such as laponite, vermiculite, bentonite, kaolinite, illite, halloysite, cloisite, or an organoclay such as a synthetic or naturally-occurring clay bearing surface amine functionality, for example a synthetic or naturally-occurring clay modified with a silane coupling agent containing an amine group (e.g. an amino-functionalized magnesium phyllosilicate clay), or mixtures thereof.
  • the nanoclay comprises laponite or bentonite, preferably laponite.
  • Laponite is known in the art and is a synthetic hectorite made up of disc shaped nanocrystals having the general formula Na +07 [(Si 8 Mg 5.5 Lio .3 ) 0 2 o(OH) 4 ] 07 . Laponite exhibits regions of both a net negative surface charge and net positive surface charge, where the faces of the crystals have a net negative charge and the edges have a net positive charge. This makes laponite a particularly effective nanoclay for use in coating compositions as described herein where cross-links with the hydrogel forming polymer and cross-linking or nutrient salts in the composition may improve mechanical and nutrient release properties of the coating.
  • nanoclay may comprise a combination of different nanoclays, it is preferred that the nanoclays are each formed from crystals of single type of clay materials, rather than mixed layer clays in which layers of different clay types are present in the same structure.
  • the organoclay may be formed by incorporating the organic component into the clay during synthesis of the clay, or alternatively by surface modification of the clay.
  • a silane coupling agent containing an amine group may be incorporated during synthesis of a clay to produce an amine-functionalised organoclay.
  • the hydrogel forming polymer and the nanoclay are selected so as to have opposing net surface charge
  • the hydrogel forming polymer comprises a polymer having a net positive surface charge such as chitosan, poly(ethylenimine), poly(2-dimethyl(aminoethyl)methacrylate), poly(l-lysine), or combinations thereof and the nanoclay has a net negative surface charge, such as laponite, montmorillonite, bentonite, kaolinite, illite, halloysite, or combinations thereof.
  • hydrogel forming polymer having a net negative surface charge may be used, such as alginate, in combination with a nanoclay having a net positive surface charge such as a synthetic or naturally-occurring clay bearing surface amine functionality (the surface charge of which may for example be tailored by further functionalisation or pH) or laponite.
  • the hydrogel forming polymer and the nanoclay may preferably be selected so as to have corresponding net surface charge, and are provided with an oppositely charged cross-linking agent such as a cation or anion of a salt as defined herein, for example wherein the hydrogel forming polymer comprises a polymer having a net negative surface charge such as alginate and a nanoclay having a net negative surface charge such as laponite, montmorillonite, bentonite, kaolinite, illite, halloysite, or combinations thereof preferably comprising laponite.
  • hydrogel forming polymer having a net positive surface charge such as chitosan, poly(ethylenimine), poly(2-dimethyl(aminoethyl)methacrylate), poly(l-lysine), or combinations thereof may be used with a nanoclay having a net positive surface charge such as a synthetic or naturally-occurring clay bearing surface amine functionality or laponite.
  • the hydrogel forming polymer and nanoclay can be selected so that the synergistic cross-linking effect of the polymer and nanoclay may be enhanced as a result of their net surface charge, leading to improved mechanical properties of the swollen hydrogel on the seed when planted.
  • a cross-linking agent and/or a nutrient component is provided in the seed coating.
  • a cross-linking agent can provide additional cross-linking in the structure of the coating in addition to cross-linking that may be provided by the combination of the nanoclay and the hydrogel forming polymer.
  • the cross-linking agent and/or nutrient component may comprise any suitable compounds.
  • the cross-linking agent and/or nutrient component comprises a salt [Cat n+ ] x [A m ] y , for example where Cat n+ represents Na + , Ca 2+ , Mg 2+ , Sr 2+ , Ba 2+ , Cu 2+ , Fe 2+ , Fe 3+ , Co 2+ , Mn 2+ , Mo 6+ , Zn 2+ , NH 4 + or combinations thereof, preferably wherein Cat n+ comprises Ca 2+ ; and/or wherein A m_ is preferably selected from Cl , Br, V, F _ , CO 3 2 , NO 3 , SO 4 2 , BO 3 3 , a phosphate, a complexing agent such as EDTA, oxalate, citrate, glucono delta-lactone (GDL), acetate, or combinations thereof.
  • the cross-linking agent and/or nutrient component may also be provided in the form of an acid, i.e. a salt in which one or more of the cations is a hydrogen ion, for example hydrogen containing borate salts such as boric acid (H 3 BO 3 ), phosphate anions such as HPO 4 2 or H 2 PO 4 .
  • the cross-linking agent and/or nutrient component comprises a divalent or trivalent metal cation, which may suitably act as a cross-linker in the coating composition.
  • the cross-linking agent and/or nutrient component may comprise CaC , CaEDTA/GDL, CaEDTA/acetic acid, CaCOs/GDL, CaCOs/acetic acid, H 3 BO 3 , MnCh, ZnS04, Na2Mo04, CUSO4, Co(NOs)2, (NH4)6Mq7q24, EDTA iron(lll) sodium salt, ammonium iron(lll) citrate, calcium borate, nitrates such as calcium nitrate, phosphates, or combinations thereof.
  • the cross-linking agent and nutrient component may comprise the same or different compounds, for example the cross-linking agent may comprise a salt, the cation and/or anion of which acts as both a nutrient component for the seed and a cross-linker, or the cation and anion of the salt may be selected so that one of the cation or anion acts as a cross-linker, while the other of the cation or anion acts as a nutrient component.
  • the cross linker and/or nutrient component may also comprise a mixture of salts so as to provide a mixture of different cations and anions, for example to provide cross-linking as well as one or more nutrient components (for example to provide multiple different nutrient ions within the coating).
  • the cross-linking agent may preferably comprise a calcium salt.
  • salts or ions may be included to benefit other components of the coating, for example salts or ions that promote the growth or survival of biostimulant microorganisms in the coating, such as algae, fungi or bacteria.
  • the salt of the cross-linking agent and nutrient component may comprise a complexing or chelating agent such as EDTA, oxalate, citrate, glucono delta-lactone (GDL), acetate, or combinations thereof.
  • a complexing or chelating agent such as EDTA, oxalate, citrate, glucono delta-lactone (GDL), acetate, or combinations thereof.
  • the cross-linking agent, and/or a nutrient component may be provided in the seed coating in any suitable way, and may for example be provided on the seeds prior to coating with the coating composition, or said cross-linking agent and/or nutrient component may be provided in the coating composition.
  • a chelating agent such as described herein may slow gelation of the composition to avoid premature gelation of the coating composition during the coating step.
  • a cross-linking agent and/or a nutrient component is pre-coated onto the seeds before the hydrogel forming polymer and nanoclay coating composition, for example by dip coating the seeds in an aqueous solution of the cross-linking agent and/or a nutrient component and drying.
  • This pre-coating allows the hydrogel and nanoclay to form a crosslinked coating upon contact with the seed coated with the cross-linker.
  • the amount of cross-linker pre-coated onto seeds may be controlled so as to control the thickness of the hydrogel polymer-nanoclay layer that is formed the seed.
  • the cross-linking agent on the seed diffuses through the hydrogel-nanoclay layer as it forms, to promote additional growth of the coating, leading to a thicker coating layer being possible.
  • pre-coating layers can be applied to the seed prior to coating the seed with a hydrogel forming polymer and nanoclay as described herein.
  • Such pre-coating layers may suitably either combine with the coating composition comprising the hydrogel forming polymer and nanoclay or will otherwise not interfere with transfer of water and/or nutrients from the hydrogel/nanoclay coating to the seed.
  • pre-coating layers may provide only a thin film on the seed that either combines with the hydrogel/nanoclay layer during its formation, or is permeable to water and nutrients in the hydrogel/nanoclay layer.
  • the cross-linking agent and/or a nutrient component is applied over the hydrogel forming polymer and nanoclay coating composition.
  • seeds may be coated with the hydrogel forming polymer and nanoclay coating composition, and then coated with the cross-linking agent and/or a nutrient component.
  • the cross-linking agent and/or a nutrient component may preferably be coated onto the seeds in a slurry (e.g. an aqueous slurry) with a singulating agent such as talc.
  • the method may comprise optionally coating seeds with a cross-linking agent and/or a nutrient component, coating the seeds with the hydrogel forming polymer and nanoclay coating composition, then coating the seeds with a slurry comprising the cross-linking agent and/or a nutrient component.
  • the cross-linking agent and/or a nutrient component slurry may comprise the cross-linking agent and/or a nutrient component, a singulating agent, such as talc, water and optionally a dye.
  • the coated seeds may then be coated with a further layer of the hydrogel forming polymer and nanoclay coating composition, followed by a further layer of the slurry comprising the cross-linking agent and/or a nutrient component.
  • Alternate coating steps of the hydrogel forming polymer and nanoclay coating composition and the cross-linking agent and/or a nutrient component slurry may be performed to provide a plurality (for example 3 or more, preferably 4 or more such as at least 5) of layers of each of the hydrogel forming polymer and nanoclay coating composition and the cross-linking agent and/or a nutrient component.
  • the coating steps may be performed sequentially in a rotary coater (or other suitable coating apparatus) without removing the coated seeds from the apparatus, for example for drying (however it will be appreciated that the coating process may comprise drying, for example with compressed air as the seeds rotate within the rotary coater), and in some preferred embodiments, the seeds are removed after sequential addition of at least one, preferably at least three, more preferably at least four or at least five, repetitions of coating the seeds with the hydrogel forming polymer and nanoclay coating composition, then coating the seeds with a slurry comprising the cross-linking agent and/or a nutrient component.
  • the alternate coating steps of the hydrogel forming polymer and nanoclay coating composition and the cross-linking agent and/or a nutrient component slurry may be repeated on the coated seeds followed by drying outside the apparatus (preferably at least three alternate coating processes separated by two drying steps).
  • a cross- linking agent and/or a nutrient component slurry coating is used over or between layers of the hydrogel forming polymer and nanoclay coating composition
  • the seeds may in some preferred embodiments not be pre-coated with the cross-linking agent and/or a nutrient component. It has been surprisingly found that applying a cross-linking agent and/or a nutrient component in a slurry coating, for example between each of a plurality of hydrogel forming polymer and nanoclay coating composition layers, increases stability of the seed coating.
  • the coating composition comprising the hydrogel forming polymer and the nanoclay may be coated onto the seed in any suitable way.
  • the coating composition comprises a solution or suspension of the hydrogel forming polymer and nanoclay, preferably an aqueous solution or suspension.
  • the solution or suspension may be applied to the seed by known processes such as by dip coating or rotary coating.
  • the first coating layer is applied by dip coating, which permits a cross-linking agent on the surface of the seed to promote growth of the first coating layer, where the thickness of the first coating layer may suitably be controlled by controlling the quantity of cross-linking agent present on the seed as described herein.
  • the seeds may be coated by alternately rotary coating with a solution or suspension of the hydrogel forming polymer and nanoclay and a slurry comprising a singulating agent.
  • the coating composition may suitably comprise the hydrogel forming polymer in any suitable amount to provide the coating. It will be appreciated that the concentration of hydrogel forming polymer in an aqueous coating composition may be limited in order to avoid excessive viscosity or gelation prior to coating the seeds.
  • the coating composition comprises the hydrogel forming polymer in an amount of from 1 mM to 500 mM, preferably from 5 mM to 200 mM, more preferably from 10 mM to 100mM, for example from 25 mM to 75 mM.
  • the coating composition may comprise the hydrogel forming polymer in an amount of no more than 500 mM, preferably no more than 200 mM, for example no more than 100 nM or no more than 75 mM.
  • the coating composition may comprise the hydrogel forming polymer in an amount of at least 1 mM, preferably at least 5 mM, for example at least 10 mM or at least 25 mM.
  • the coating composition may comprise the hydrogel forming polymer in an amount of from 0.1 wt.% to 5 wt.%, preferably from 0.3 wt.% to 3 wt.%, more preferably from 0.5 wt.% to 2 wt.%, for example from 0.7 wt.% to 1.5 wt.%.
  • the coating composition may comprise the hydrogel forming polymer in an amount of at least 0.1 wt.%, preferably at least 0.3 wt.%, more preferably at least 0.5 wt.%, for example at least 0.7 wt.%.
  • the coating composition may comprise the hydrogel forming polymer in an amount of no more than 5 wt.%, preferably no more than 3 wt.%, more preferably no more than 2 wt.%, for example no more than 1.5 wt.%
  • the coating composition may suitably comprise the nanoclay in any suitable amount to provide the coating.
  • the concentration of the nanoclay in the coating composition may be adjusted to provide suitable viscosity of the coating composition.
  • the coating composition comprises the nanoclay in an amount of from 0.05 w/v% to 3.0 w/v%, preferably from 0.1 w/v% to 1.5 w/v%, for example from 0.2 w/v% to 1.0 w/v%.
  • the coating composition may comprise the nanoclay in an amount of no more than 3.0 w/v%, preferably no more than 1.5 w/v%, for example no more than 1.0 w/v%.
  • the coating composition may comprise the nanoclay in an amount of at least 0.01 w/v%, preferably at least 0.05 w/v%, for example at least 0.1 w/v% or at least 0.2 w/v%.
  • the cross-linking agent and/or a nutrient component may be provided in any suitable amount and may be adjusted to provide suitable cross-linking and to meet the nutritional needs of the seed.
  • some ions or salts, such as divalent or trivalent metal ions may be present in an amount to provide a cross linking effect in the coating, while other ions may be present in lower amounts, for example in only trace amounts, depending on the needs of the seed and the environment it is to be planted in.
  • the cross-linking agent and/or a nutrient component is provided in a precoating solution or the coating composition or a slurry coating composition in an amount of from 10 mM to 500 mM, preferably from 20 mM to 300 mM, more preferably from 50 mM to 200 mM, for example from 75 mM to 125 mM.
  • the cross-linking agent and/or a nutrient component is provided in a precoating solution or the coating composition in an amount of no more than 500 mM, preferably no more than 300 mM, for example no more than 200 mM or no more than 125 mM.
  • the cross-linking agent and/or a nutrient component is provided in a precoating solution or the coating composition in an amount of at least 10 mM, preferably at least 20 mM, for example at least 50 mM or at least 75 mM.
  • the amount of cross-linking agent and/or a nutrient component actually provided on the seed may be adjusted by using a higher concentration or by providing multiple pre coats or slurry coats of the cross-linking agent and/or nutrient component.
  • the coating composition further comprises a biostimulant, such as a biostimulant microorganism, for example an algae preferably selected from Anabaena, Nostoc, Chlorogloepsis, Clamidomona reinhardtii, Ascophyllum nodosum, Spirulina (Arthrospira platensis), a fungi such as Mycorrhiza ECM or Suillos tormentosos or a bacteria such as beijerinckiaceae or rhizobia, or extracts from such microorganisms, for example algae extracts containing salts and/or micronutrients such as vitamins and minerals, or any other suitable non-microorganism biostimulants or fertilisers.
  • a biostimulant microorganism for example an algae preferably selected from Anabaena, Nostoc, Chlorogloepsis, Clamidomona reinhardtii, Ascophyllum nodosum, Spirulina (Art
  • Non-microbial biostimulants may for example include seaweed (such as Ascophyllum nodosum) or algal extracts, amino acids such as proline, hydroxyproline, glutamate or glycine, humic and/or fulvic acids, plant hormones such as gibberellic acid, auxins or cytokinins, or vitamins, polysaccharides or lipids.
  • seaweed such as Ascophyllum nodosum
  • algal extracts amino acids such as proline, hydroxyproline, glutamate or glycine
  • humic and/or fulvic acids such as gibberellic acid, auxins or cytokinins
  • plant hormones such as gibberellic acid, auxins or cytokinins
  • vitamins polysaccharides or lipids.
  • a biostimulant for example a seaweed or algal extract, may suitably contain nutrients such as calcium (for example 0.5 to 5 %), chlorine (for example 1 to 5 %), magnesium (for example 0.2 to 3 %), nitrogen (for example 0.1 to 2 %), phosphorous (for example 0.01 to 0.3 %), potassium (for example 0.5 to 5 %), sodium (for example 1 to 5 %), sulfur (for example 0.2 to 5 %), barium (for example 10 to 500 ppm), boron (for example 10 to 500 ppm), copper (for example 1 to 30 ppm), iodine (for example 200 to 2000 ppm), iron (for example 10 to 500 ppm), manganese (for example 1 to 100 ppm), selenium (for example 0.5 to 20 ppm) and/or zinc (for example 1 to 100 ppm).
  • nutrients such as calcium (for example 0.5 to 5 %), chlorine (for example 1 to 5 %), magnesium (for example 0.2 to 3 %), nitrogen (
  • the biostimulant may also comprise other active agents such as auxins, betaines, cytokinins, alginic acid, mannitol, laminarian, amino acids and/or vitamins.
  • the biostimulant for example where the biostimulant comprises a plant extract such as a seaweed extract, may comprise alginate, preferably in an amount of less than 50 %, for example less than 40 %.
  • a total amount of alginate or hydrogen-forming polymer in the coating composition as specified herein will suitably include alginate derived from the biostimulant component.
  • the coating may comprise a biocide such as a fungicide, a herbicide, an insecticide, or a microbicide.
  • the seed coating, or a first layer of the seed coating consists essentially of the hydrogel forming polymer, the nanoclay and the cross-linking agent and/or a nutrient component, and optionally comprises additionally non-structural components such as dyes, biostimulants such as biostimulant microorganisms or extracts, fungicides or microbicides.
  • the seed coating comprises or consists essentially of at least one layer consisting essentially of the hydrogel forming polymer, the nanoclay and optionally non-structural components such as dyes, biostimulants such as biostimulant microorganisms or extracts, fungicides or microbicides, and at least one further layer comprising or consisting essentially of the cross-linking agent and/or a nutrient component, a singulating agent and optionally non-structural components such as dyes, biostimulants such as biostimulant microorganisms or extracts, fungicides or microbicides.
  • non- structural components such as dyes, biostimulants such as biostimulant microorganisms or extracts, fungicides or microbicides are present in a layer comprising or consisting essentially of the cross-linking agent and/or a nutrient component and a singulating agent.
  • the method comprises one or more steps of applying at least one further coating layer to the coated seeds.
  • the further coating layer or layers may suitably be provided on the first coating layer following drying of the coated seeds, and/or may be provided prior to drying the coated seeds.
  • a plurality of coating layers are applied without drying the coated seeds (or without removing the seeds from the coating apparatus, and optionally drying in situ such as using compressed air), followed by drying, then applying another plurality of coating layers to the dried seeds (and optionally repeating after one or more further drying steps).
  • the at least one further coating layer suitably comprises a second coating composition, for example wherein the second coating composition comprises a hydrogel forming polymer and nanoclay as defined herein in relation to the first coating layer, preferably the second coating composition comprises the same hydrogel forming polymer and nanoclay as are present in the coating of the coated seeds to which the further coating layer or layers are applied.
  • the second coating composition comprises a hydrogel forming polymer and nanoclay as defined herein in relation to the first coating layer
  • the second coating composition comprises the same hydrogel forming polymer and nanoclay as are present in the coating of the coated seeds to which the further coating layer or layers are applied.
  • each layer may comprise the same or a different coating composition.
  • each further layer comprises the same coating composition.
  • the further coating layer is suitably provided in addition to a layer comprising or consisting essentially of the cross-linking agent and/or a nutrient component and a singulating agent, which may for example be applied as a layer separating each further layer comprising a hydrogel forming polymer and nanoclay.
  • one or more steps of applying at least one further coating layer to the coated seeds may comprise: (i) coating the coated seeds with a slurry comprising the cross-linking agent and/or a nutrient component and a singulating agent; then (ii) applying a further coating layer comprising a hydrogel forming polymer and nanoclay as defined in any one of the preceding claims, preferably same hydrogel forming polymer and nanoclay as are present in the coating of the coated seeds; and (ii) optionally repeating steps (i) and (ii) to provide a plurality of coating layers.
  • the further coating layer or layers are applied by rotary coating the coated seeds with the second coating composition.
  • the at least one further coating layer may be applied by other methods such as by dip coating.
  • a singulating agent is added during the further coating step, for example talc, clay powders such as nanoclays, or a combination thereof. This prevents clumping of the coated seeds during the coating step.
  • the singulating agent may in some preferred embodiments be applied as a slurry (e.g. an aqueous slurry), which may comprise a cross-linking agent and/or a nutrient component. In some embodiments, the singulating agent is applied as a slurry without a cross-linking agent and/or a nutrient component.
  • a singulating agent may nonetheless also be applied as a powder (i.e. not as a slurry) between each step of coating a seed with a slurry or a coating layer comprising a hydrogel forming polymer and nanoclay.
  • the second coating composition may comprise one or more suitable dyes for providing colour to the coated seeds.
  • the dye may be selected and added in an amount so as not to interfere with the structure or function of the seed coating.
  • suitable dyes or pigments for seed coatings are known in the art, such as water-based liquid pigment dispersions available as SensiCoat (from Sensient), pigment dispersions or powers available as Agrocer (from Clariant), or non-resinated pigment dispersions available as Chromatech (from Chromatinit).
  • dyes may in some preferred embodiments be applied with a slurry of a singulating agent between coating layers of a hydrogel forming polymer and the nanoclay coating composition.
  • the second coating composition does not comprise a cross-linking agent, such as a precoated cross-linking agent, as may be present in the first coating layer.
  • a cross-linking agent such as a precoated cross-linking agent
  • this may provide a nucleation site for adhering the further coating layer to the first coating layer.
  • applying a cross-linking agent in a slurry with a singulating agent between layers of hydrogel forming polymer and nanoclay can improve stability.
  • the at least one further coating layer may be provided on the coated seed so as to improve the handling properties of the seeds as well as to provides a protective barrier around the coated seed (for example to prevent damage to the first coating layer during transit or planting).
  • the further coating layer may also serve to lock in moisture present in the seed to avoid water loss prior to or after planting, for example moisture may be imparted into seeds during a pre-chilling process (known as moist chilling or cold stratification), and locked in by the provision of coatings as described herein.
  • Pre-chilling of seeds is known in the art and typically involves soaking the seed in water to imbibe water into the seed which improves germination rate and breaks seed dormancy.
  • a pre-chilling step may be performed by placing seeds in mesh fabric bags and immersing them in cold water, then keeping them in a fridge at 4 °C for approximately two days (where the water is changed after 1 day).
  • the seeds may be kept in moist cold conditions for several weeks following this.
  • the seeds can be surface dried, for example by placing them on a sieved mesh or an absorbent material such as an absorbent paper.
  • the method may suitably comprise any other suitable see priming method prior to the present coating method, such as are for example described in Lutts, S. et al.
  • the further coating layer or layers may be provided so as to produce coated seed pellets, which may comprise encrusted seeds, which maintain the general shape of the seed, or rounded (e.g. substantially spherical) pills or pellets where sufficient coating is added to hide the shape of the seed within the rounded pill or pellet.
  • the at least one further coating layer has a thickness of at least about 0.5 mm and/or provides a weight increase of at least 50%, preferably at least 100% relative to the uncoated seed, so as to form coated seed pellets.
  • the total amount of coating may be varied by varying the amount of material coated onto the coated seeds in a single step or by applying multiple further layers of coating in separate steps.
  • the seeds that are coated may be any suitable seeds.
  • the seeds are forestry seeds, such as Pinus sylvestris, agricultural seeds, such as oilseed, vegetable seed, cereal crops such as wheat, barley or corn, or horticultural seeds such as wildflowers or grass seed. Nonetheless, it will be appreciated that the coatings described herein may suitably be applied to any seed for which the coating is desired.
  • the seed coating described herein may absorb water and swell to form a hydrogel coating that provides a reservoir of water to the seed.
  • the method may comprise swelling the seed coating with water to form a hydrogel coating. It will be appreciated that this step may happen naturally in the ground after planting by absorption of water in the ground, or by watering the seeds during planting. It is preferred that the seed coating is not swelled with water prior to planting as this can lead to clumping of seeds and cause difficulties in handling and planting seeds.
  • the coating of the seed may alternatively or additionally contain sufficient water prior to planting and/or reduce loss of water from the seed to protect against water stress.
  • a further aspect provides a coated seed prepared by any of the methods described herein.
  • a further aspect provides a seed coated with a coating layer comprising a hydrogel forming polymer and a nanoclay.
  • the seed and/or the seed coating for example the hydrogel forming polymer and nanoclay, or any other materials present in the coating and any further coating layers, may be substantially as defined previously herein.
  • a further aspect provides the use of a seed coating comprising a hydrogel forming polymer and a nanoclay for providing hydration and/or nutrients to seeds, for example after planting the seeds.
  • a seed coating comprising a hydrogel forming polymer and a nanoclay for providing hydration and/or nutrients to seeds, for example after planting the seeds.
  • the seed and/or the seed coating for example the hydrogel forming polymer and nanoclay, or any other materials present in the coating and any further coating layers, may be substantially as defined previously herein.
  • Figure 1 is a photograph of coated seeds that have been immersed in water to swell the seed coating
  • Figures 2a and 2b show photographs of coated seeds before and after additional coating steps to form larger seed pellets
  • Example 1 First coating layer
  • the CaCh treated seeds from the above step were submerged in an aqueous seed coating composition (4000 ml) containing alginate (50 mM; viscosity of 15-25 cP at 1% in H2O) and Laponite RD (0.5 w/v%) for 5 minutes. Following this the seeds were recovered and allowed to air dry overnight.
  • Figure 1 is a photograph of the coated seeds that have been immersed in water, showing swelling of the coating 102 to provide a water reservoir to the seed 101.
  • Example 2 Second coating layer
  • Example 2 The coated seeds from Example 1 (which have not been immersed in water to swell the coating) were all combined and coated using a rotary coater, which was used to apply, in a single coating step, 10 g talc and 20 ml of an aqueous coating composition containing 50 mM alginate (viscosity of 15-25 cP at 1% in H2O), 0.5 w/v% Laponite RD, and 2 w/v% Sensicoat Blue dye.
  • the coated seeds from Example 2 were coated using a rotary coater, which was used to apply, in a single coating step, 371.4 g talc and 120 ml of an aqueous coating composition containing 50 mM alginate (viscosity of 15-25 cP at 1% in H2O), 0.5 w/v% Laponite RD, and 2 w/v% Sensicoat Blue dye.
  • Figures 2a and 2b show photographs of coated seeds produced according to Examples 2 and 3, respectively. As can be seen, the coated seeds in Figure 2b are in the form of larger pellets or encrusted seeds and only approximately retain the shape of the original seeds.
  • Example 4 Seed coating using calcium-containing slurry
  • talc powder (0.3 g) was added to the rotary coater to provide a talc layer;
  • talc powder (0.3 g) was added to the rotary coater to provide a talc layer;
  • steps (i) to (v) were repeated four more times and the coated seeds transferred to a petri dish to dry.
  • the method (i) to (vi) was repeated a further two times (three times total) by using the dried coated seeds from step (vi) as the seeds added prior to step (i).
  • the coated seeds were found to increase in mass from 19 g to 58.2 g by three repetitions of the above coating process.
  • the coating was found to have good water stability and increased build-up of layers (by mass) compared to the same process in which the slurry did not contain CaCh (up to - 49 g after coating).
  • an aqueous calcium chloride solution was used in place of the slurry in step (iii)
  • build-up of layers was much slower and less growth of coating layers could be achieved (up to - 27 g after coating).
  • talc powder (0.3 g) was added to the rotary coater to provide a talc layer;
  • talc powder (0.3 g) was added to the rotary coater to provide a talc layer;
  • step (i) to (vi) was repeated a further two times (three times total) by using the dried coated seeds from step (vi) as the seeds added prior to step (i).
  • the coated seeds were found to increase in mass from 19 g to 36.1 g by three repetitions of the above coating process.
  • the coated seeds were found to have very good water stability and coverage of the seeds despite lower layer growth and absence of calcium in the slurry used in step (iii).
  • Example 6 Seed coating using carboxymethylcellulose
  • aqueous coating composition (-0.5 ml) containing 1 w/v% low viscosity sodium carboxymethylcellulose (viscosity of 4% aqueous solution at 25 °C of 20 to 50 mPa.s, using Brookfield LV rotational viscometer at 60 rpm), 0.5 w/v% Laponite RD and 2 wt.% Chromatint Blue dye was added to coat the seeds;
  • talc powder (0.5 g) was added to the rotary coater to provide a talc layer;
  • steps (i) to (iii) were repeated four more times and the coated seeds transferred to a petri dish to dry.
  • the method (i) to (iv) was repeated a further two times (three times total) by using the dried coated seeds from step (vi) as the seeds added prior to step (i).
  • the coated seeds were found to increase in mass from 19 g to 30.1 g by three repetitions of the above coating process.
  • the coated seeds were found to have smooth coverage of the seeds, though water stability was not as good as the coatings of Examples 4 and 5.
  • Pinus sylvestris seeds (0.5 g) were immersed in 20 ml of 0.5 M CaCh for 5 minutes, then were recovered and allowed to air dry in a petri dish for 30 minutes.
  • the dried CaCh treated seeds were submerged in an aqueous seed coating composition (10 ml) of an aqueous coating composition containing alginate (50 mM; viscosity of 15-25 cP at 1% in H2O) and 0.5 wt.% of a powdered mixture of organically modified bentonite and xanthan gum (specific density 2.2 g/cm 3 , loose bulk density 530-650 g/l, pH 9-11 as 2% suspension in water, max 13% water content) for 10 minutes. Following this the seeds were recovered and allowed to air dry in a petri dish. When the dried coated seeds were immersed in water, the seed coating swells to provide a hydrogel coating around the seed.
  • Example 8 - Seed coating comprising biostimulant
  • Example 2 The method of Example 1 was repeated with the addition of 10 w/v% of seaweed extract (Ascophyllum nodosum) in the coating composition as a biostimulant.
  • the seaweed extract contained ca. 30 % alginate as well as calcium (1.95 %); chlorine (3.42 %), magnesium (1.23 %), nitrogen (0.62 %), phosphorous (0.12 %), potassium (2.11 %), sodium (3.10 %), sulphur (1.56 %), barium (127 ppm), boron (194 ppm), copper (6 ppm), iodine (1200 ppm), iron (211 ppm), manganese (22 ppm), selenium (4 ppm), zinc (35 ppm).
  • the seaweed extract also contained auxins, betaines, cytokinins, alginic acid, mannitol, laminarian, amino acids and vitamins.
  • the coated seeds were found to swell upon immersion in water showing that the addition of the biostimulant is compatible with the swelling coating composition.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Pretreatment Of Seeds And Plants (AREA)

Abstract

L'invention concerne un procédé d'enrobage de semences, le procédé consistant à fournir une composition d'enrobage comprenant un mélange d'un polymère formant un hydrogel et une nanoargile, et à enrober des semences à l'aide de la composition d'enrobage. L'invention concerne également des semences enrobées comportant une couche d'enrobage comprenant un polymère formant un hydrogel et une nanoargile, et l'utilisation d'un enrobage de semences comprenant un polymère formant un hydrogel et une nanoargile pour fournir une hydratation et/ou des nutriments aux semences.
PCT/GB2022/051777 2021-07-09 2022-07-08 Semences enrobées et procédé de préparation de semences enrobées Ceased WO2023281280A1 (fr)

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Cited By (1)

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WO2024231398A1 (fr) 2023-05-11 2024-11-14 Agriodor Semences enrobées d'un mélange de composés organiques volatils (cov) répulsifs

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EP2840074A1 (fr) * 2013-08-23 2015-02-25 Biotensidon GmbH Préparation destinée à soutenir la culture des plantes, son utilisation et son procédé de fabrication
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024231398A1 (fr) 2023-05-11 2024-11-14 Agriodor Semences enrobées d'un mélange de composés organiques volatils (cov) répulsifs
FR3148508A1 (fr) 2023-05-11 2024-11-15 Agriodor Semences enrobees avec un melange repulsif de cov

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